The maize rp1 rust resistance gene identifies homologues in barley that have been subjected to diversifying selection |
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Authors: | MA Ayliffe NC Collins JG Ellis A Pryor |
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Institution: | (1) CSIRO Plant Industry, P.O. Box 1600, Canberra, ACT, Australia 2601, Fax: +6102 62465000, e-mail: michaela@pi.csiro.au, AU |
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Abstract: | A number of agronomically important grasses (sorghum, wheat, panicum, sugar cane, oats, rice and barley) are shown to contain
sequences homologous to rp1, a maize gene that confers race-specific resistance to the rust fungus Puccinia sorghi. Mapping of rp1-related sequences in barley identified three unlinked loci on chromosomes 1HL, 3HL and 7HS. The locus located on chromosome
7HS comprises a small gene family of at least four members, two of which were isolated and are predicted to encode nucleotide
binding site-leucine-rich repeat (NBS-LRR) proteins that are respectively 58% and 60% identical to the maize rp1 protein. Evidence of positive selection for sequence diversification acting upon these two barley genes was observed; however,
diversifying selection was restricted to the carboxy terminal half of the LRR domain. One of these rp1 homologous genes cosegregated with the barley Rpg1 stem rust resistance gene amongst 148 members of the Steptoe × Morex double haploid mapping family. Three other unrelated
resistance gene-like sequences, potentially encoding NBS-LRR proteins, are also shown to be linked to the Rpg1 locus but not cosegregating with the gene.
Received: 2 August 1999 / Accepted: 28 September 1999 |
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Keywords: | Rust resistance rp1 Barley Maize Rpg1 Puccinia |
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